REG_SMSTA
reg_write(smbus, REG_SMSTA, status);
status = reg_read(smbus, REG_SMSTA);
ioread32, smbus->ioaddr + REG_SMSTA,
reg_write(smbus, REG_SMSTA, SMSTA_XEN);
ret = readx_poll_timeout(ioread32, smbus->ioaddr + REG_SMSTA,